The patch titled
Subject: lib/ubsan.c: don't handle misaligned address when kernel supports unaligned access
has been added to the -mm tree. Its filename is
ubsan-dont-handle-misaligned-address-when-support-unaligned-access.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/ubsan-dont-handle-misaligned-address-when-support-unaligned-access.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/ubsan-dont-handle-misaligned-address-when-support-unaligned-access.patch
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------------------------------------------------------
From: Ding Tianhong <dingtianhong@xxxxxxxxxx>
Subject: lib/ubsan.c: don't handle misaligned address when kernel supports unaligned access
ubsan reports a warning like:
UBSAN: Undefined behaviour in ../include/linux/etherdevice.h:386:9
load of misaligned address ffffffc069ba0482 for type 'long unsigned int'
which requires 8 byte alignment
CPU: 0 PID: 901 Comm: sshd Not tainted 4.xx+ #1
Hardware name: linux,dummy-virt (DT)
Call trace:
[<ffffffc000093600>] dump_backtrace+0x0/0x348
[<ffffffc000093968>] show_stack+0x20/0x30
[<ffffffc001651664>] dump_stack+0x144/0x1b4
[<ffffffc0016519b0>] ubsan_epilogue+0x18/0x74
[<ffffffc001651bac>] __ubsan_handle_type_mismatch+0x1a0/0x25c
[<ffffffc00125d8a0>] dev_gro_receive+0x17d8/0x1830
[<ffffffc00125d928>] napi_gro_receive+0x30/0x158
[<ffffffc000f4f93c>] virtnet_receive+0xad4/0x1fa8
The reason is that when enabling the CONFIG_UBSAN_ALIGNMENT, ubsan will
report the unaligned access even if the system supports it
(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS=y). This produces a lot of noise
in the log and causes confusion.
Prevent the detection of unaligned access when the system support
unaligned access.
Link: http://lkml.kernel.org/r/5b905d56-609e-3822-096a-3b93b3eb7675@xxxxxxxxxx
Signed-off-by: Ding Tianhong <dingtianhong@xxxxxxxxxx>
Cc: David Laight <David.Laight@xxxxxxxxxx>
Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
lib/ubsan.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff -puN lib/ubsan.c~ubsan-dont-handle-misaligned-address-when-support-unaligned-access lib/ubsan.c
--- a/lib/ubsan.c~ubsan-dont-handle-misaligned-address-when-support-unaligned-access
+++ a/lib/ubsan.c
@@ -322,7 +322,8 @@ void __ubsan_handle_type_mismatch(struct
if (!ptr)
handle_null_ptr_deref(data);
else if (data->alignment && !IS_ALIGNED(ptr, data->alignment))
- handle_missaligned_access(data, ptr);
+ if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS))
+ handle_missaligned_access(data, ptr);
else
handle_object_size_mismatch(data, ptr);
}
_
Patches currently in -mm which might be from dingtianhong@xxxxxxxxxx are
ubsan-dont-handle-misaligned-address-when-support-unaligned-access.patch
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